Container structure for removal of vacuum pressure

ABSTRACT

A hot-fill PET container or bottle ( 10 ) filling with a liquid at an elevated temperature has a side wall ( 9 ) extending to a lower portion including a pressure panel ( 11 ) and a base ( 21 ) in its unfolded or pre-fill position. The panel ( 11 ) is transversely oriented and has a decoupling or hinge structure ( 13 ), an initiator portion ( 1 ) and control portion ( 5 ) of a steeply angled inverting conical section between 30 and 45 degrees. The control portion enables the inversion of the panel ( 11 ) into the container ( 10 ) to compensate for vacuum or reduced pressure induced within the container as the liquid cools down. The base ( 2 ) can also have a plurality of reinforcing ribs ( 3 ).

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of Ser. No. 10/529,198, filed Dec.15, 2005, published as US2006/0138074, now U.S. Pat. No. 8,152,010,which is a Section 371 of PCT/NZ03/00220, filed Sep. 30, 2003, publishedas WO/2004/028910, which claims priority to NZ521694 filed Sep. 30,2002, the content of all of which are hereby incorporated by reference.

FIELD

This invention relates generally to a container structure that allowsfor the removal of vacuum pressure. This is achieved by inverting atransversely oriented vacuum pressure panel located in the lowerend-wall, or base region of the container.

BACKGROUND

So called ‘hot fill’ containers are well known in prior art, wherebymanufacturers supply PET containers for various liquids which are filledinto the containers and the liquid product is at an elevatedtemperature, typically at or around 85 degrees C. (185 degrees F.).

The container is manufactured to withstand the thermal shock of holdinga heated liquid, resulting in a ‘heat-set’ plastic container. Thisthermal shock is a result of either introducing the liquid hot atfilling, or heating the liquid after it is introduced into thecontainer.

Once the liquid cools down in a capped container, however, the volume ofthe liquid in the container reduces, creating a vacuum within thecontainer. This liquid shrinkage results in vacuum pressures that pullinwardly on the side and end walls of the container. This in turn leadsto deformation in the walls of plastic bottles if they are notconstructed rigidly enough to resist such force.

Typically, vacuum pressures have been accommodated by the use of vacuumpanels, which distort inwardly under vacuum pressure. Prior art revealsmany vertically oriented vacuum panels that allow containers towithstand the rigors of a hot fill procedure. Such vertically orientedvacuum panels generally lie parallel to the longitudinal axis of acontainer and flex inwardly under vacuum pressure toward thislongitudinal axis.

In addition to the vertically oriented vacuum panels, many prior artcontainers also have flexible base regions to provide additional vacuumcompensation. Many prior art containers designed for hot-filling havevarious modifications to their end-walls, or base regions to allow foras much inward flexure as possible to accommodate at least some of thevacuum pressure generated within the container.

All such prior art, however, provides for flat or inwardly inclined, orrecessed base surfaces. These have been modified to be susceptible to asmuch further inward deflection as possible. As the base region yields tothe force, it is drawn into a more inclined position than prior tohaving vacuum force applied.

Unfortunately, however, the force generated under vacuum to pulllongitudinally on the base region is only half that force generated inthe transverse direction at the same time. Therefore, verticallyoriented vacuum panels are able to react to force more easily than apanel placed in the base. Further, there is a lot more surface areaavailable around the circumference of a container than in the end-wall.Therefore, adequate vacuum compensation can only be achieved by placingvertically-oriented vacuum panels over a substantial portion of thecircumferential wall area of a container, typically 60% of the availablearea.

Even with such substantial displacement of vertically-oriented panels,however, the container requires further strengthening to preventdistortion under the vacuum force.

The liquid shrinkage derived from liquid cooling, causes a build up ofvacuum pressure. Vacuum panels deflect toward this negative pressure, toa degree lessening the vacuum force, by effectively creating a smallercontainer to better accommodate the smaller volume of contents. However,this smaller shape is held in place by the generating vacuum force. Themore difficult the structure is to defied inwardly, the more vacuumforce will be generated. In prior art, a substantial amount of vacuum isstill present in the container and this tends to distort the overallshape unless a large, annular strengthening ring is provided inhorizontal, or transverse, orientation at least a ⅓ of the distance froman end to the container.

Considering this, it has become accepted knowledge to believe that it isimpossible to provide for full vacuum compensation through modificationto the end-wall or base region alone. The base region offers very littlesurface area, compared to the side walls, and reacts to force at halfthe rate of the side walls.

Therefore it has become accepted practice to only expect partialassistance to the overall vacuum compensation to be generated throughthe base area. Further, even if the base region could provide for enoughflexure to accommodate all liquid shrinkage within the container, therewould be a significant vacuum force present, and significant stress onthe base standing ring. This would place force on the sidewalls also,and to prevent distortion the smooth sidewalls would have to be muchthicker in material distribution, be strengthened by ribbing or thelike, or be placed into shapes more compatible to mechanical distortion(for example be square instead of circular).

For this reason it has not been possible to provide container designs inplastic that do not have typical prior art vacuum panels that arevertically oriented on the sidewall. Many manufacturers have thereforebeen unable to commercialize plastic designs that are the same as theirglass bottle designs with smooth sidewalls.

U.S. Pat. No. 6,595,380 (Silvers), claims to provide for full vacuumcompensation through the base region without requiring positioning ofvertically oriented vacuum panels on the smooth sidewalls. This issuggested by combining techniques well-known and practiced in the priorart. Silvers provides for a slightly inwardly domed, and recessed baseregion to provide further inward movement under vacuum pressure.However, the technique disclosed, and the stated percentage areasrequired for efficiency are not considered by the present applicant toprovide a viable solution to the problem.

In fact, flexure in the base region is recognised to be greatest in ahorizontally flat base region, and maximizing such flat portions on thebase has been well practiced and found to be unable to provide enoughvacuum compensation to avoid also employing vertically oriented vacuumpanels.

Silvers does provide for the base region to be strengthened by couplingit to the standing ring of the container, in order to assist preventingunwanted outward movement of the inwardly inclined or flat portion whena heated liquid builds up initial internal pressure in a newly filledand capped container. This coupling is achieved by rib structures, whichalso serve to strengthen the flat region. Whilst this may strengthen theregion in order to allow more vacuum force to be applied to it, the ribsconversely further reduce flexibility within the base region, andtherefore reduce flexibility.

It is believed by the present applicant that the specific ‘ribbed’method proposed by Silvers could only provide for approximately 35% ofthe vacuum compensation that is required, as the modified end-wall isnot considered capable of sufficient inward flexure to fully account forthe liquid shrinkage that would occur. Therefore a strong maintenance ofvacuum pressure is expected to occur. Containers employing such basestructure therefore still require significant thickening of thesidewalls, and as this is done the base region also becomes thickerduring manufacturing. The result is a less flexible base region, whichin turn also reduces the efficiency of the vacuum compensation achieved.

The present invention relates to a hot-fill container which is adevelopment of the hot-fill container described in our internationalapplication WO 02/18213 (the PCT specification), which specification isincorporated herein in its entirety where appropriate.

The PCT specification backgrounds the design of hot-fill containers andthe problems with such designs which were overcome or at leastameliorated by the design disclosed in the PCT specification.

In the PCT specification a semi-rigid container was provided that had asubstantially vertically folding vacuum panel portion. Such atransversely oriented vacuum panel portion included an initiator portionand a control portion which generally resisted being expanded from thecollapsed state.

Further described in the PCT specification is the inclusion of thevacuum panels at various positions along the container wall.

A problem exists when locating such a panel in the end-wall or baseregion, whereby stability may be compromised if the panel does not movefar enough into the container longitudinally to no longer form part ofthe container touching the surface the container stands on.

A further problem exists when utilizing a transverse panel in the baseend-wall due to the potential for shock deflection of the inverted panelwhen a full and capped container is dropped. This may occur on acontainer with soft and unstructured walls that is dropped directly onits side. The shock deflection of the sidewalls causes a shock-wave ofinternal pressure that acts on the panel. In such cases improved panelconfigurations are desired that further prevent panel roll-out, orinitiator region configurations utilized that optimize for resistance tosuch reversion displacement.

In view of the above, it is an object of one preferred embodiment of thepresent invention to provide a plastic container structure having atransversely oriented pressure panel in its lower portion that canprovide for removal of vacuum pressure such that there is substantiallyno remaining force within the container.

It is a further object of one preferred embodiment of the presentinvention to provide a container which has a transversely orientedpressure panel that is decoupled to a degree from the adjoining wallsuch that greater inward and longitudinal movement can be achieved.

It is a further object of one preferred embodiment of the presentinvention to provide for a container to have a transversely orientedpressure panel that is inwardly displaced to a position above thestanding ring of the final container configuration, such that a new baseregion is formed with a greater standing ring or foot print area, andthe pressure panel is substantially protected from top load forceapplied to the container during commercial distribution.

It is a further object of one preferred embodiment of the presentinvention to provide for an improved transverses oriented pressure panelhaving an initiator portion which may utilize essentially the same angleas the control portion, such that greater removal of vacuum pressure canbe obtained and such that greater resistance to outward deflection canalso be obtained.

A further and alternative object of the present invention in all itsembodiments, all the objects to be read disjunctively, is to at leastprovide the public with a useful choice.

SUMMARY

According to one aspect of the present invention there is provided acontainer having a longitudinal axis, an upper portion having an openinginto said container, a body portion extending from said upper portion toa lower portion, said lower portion including a base, said base closingoff an end of said container, said container having at least onesubstantially transversely oriented pressure panel portion located insaid lower portion, said pressure panel portion being capable of foldingfrom one longitudinally inclined position to an inverted position tocompensate for a change of pressure induced within the container.

According to a further aspect of the present invention a container has alongitudinal axis and a base, and at least one substantiallytransversely oriented vacuum panel portion located adjacent to saidbase, said vacuum panel portion being adapted in use to fold from alongitudinally inclined position to an inverted position to compensatefor a change of pressure induced within the container following coolingof a liquid within the container after it has been capped, such thatless force is exerted on the internal walls of said container.

According to a further aspect of the present invention a container has alongitudinal axis, a side wall and a base closing off one end, saidcontainer having a single substantially transversely oriented vacuumpanel portion located within the base and joined to the side wall by adecoupling or hinge structure, said vacuum panel portion being adaptedin use to fold from a longitudinally inclined position to an invertedposition to compensate for 2 change of pressure induced within thecontainer.

Preferably in one embodiment the vacuum panel portion may include aninitiator section and a control section, said initiator sectionproviding for folding before said control section.

Preferably in one embodiment a decoupling structure connects thepressure panel portion with the body portion and is of an area whichallows for greater inward and upward longitudinal movement of thepressure panel.

Preferably in one embodiment the vacuum panel portion has nostrengthening ribs to restrain substantial longitudinal movement andinversion.

Preferably in one embodiment the vacuum panel portion may includefluting structures or the like to allow an even circumferentialdistribution of folding forces to provide for increased control overfolding the panel portion from one inclined position to another and toassist in preventing unwanted return to the original position.

Preferably in one embodiment after folding, the container standingsupport is provided by a lower part of the container sidewall thatprovides a replacement container standing support.

According to a further aspect of the invention a method of compensatingfor a change in pressure in a container as defined in any one of thepreceding eight paragraphs is provided in which said method includesapplying a force to the or each said panel portion to cause said foldingto occur.

According to a further aspect of this invention there is provided ahot-fill container substantially as herein described with reference toany one of the embodiments of the accompanying drawings.

Further aspects of the invention which should be considered in all itsnovel aspects will become apparent from the following description.

These and other examples are set forth more fully below in conjunctionwith drawings, a brief description of which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1: shows a cross-sectional view of a hot-fill container accordingto one possible embodiment of the invention in its pre-collapsedcondition;

FIG. 2: shows the container of FIG. 1 in its collapsed position;

FIG. 3: shows the base of FIG. 1 before collapsing;

FIG. 4: shows the base of FIG. 2 following collapsing;

FIG. 5: shows an underneath view of the base of the container of FIG. 1before collapsing.

FIG. 6: shows the base of FIG. 1 before collapsing;

FIG. 6 a: shows an alternative container configuration;

FIG. 7: shows the base of FIG. 2 following collapsing;

FIG. 8 a: shows a cross-sectional view of a hot-fill container accordingto an alternative embodiment of the invention in its pre-collapsedcondition;

FIG. 8 b: shows a side view of the container shown in FIGS. 5 b and 9through line C-C;

FIG. 9: shows an underneath view of the base of the container of FIGS. 8a and 8 b and FIG. 10 before collapsing

FIG. 10: shows a cross-sectional view of the container shown in FIG. 9through line D-D

FIGS. 11 a-d: show cross-sectional views of the container according toan alternative embodiment of the invention incorporating a pusher toprovide panel folding

FIGS. 12 a-d: show cross-sectional views of the container according to afurther alternative embodiment of the invention incorporating a pusherto provide panel folding

FIG. 13: shows the base of an alternative embodiment of the inventionbefore collapsing;

FIG. 14: shows the base of FIG. 13 during the initial stages ofcollapsing;

FIGS. 15 a-b: show side and cross-sectional views of the container shownin FIG. 9 including outwardly projecting fluting

FIG. 15 c: shows an underneath view of the base of the container ofFIGS. 15 a and 15 b with dotted contour section lines through lines E-Eand F-F;

FIG. 15 d: shows a perspective view of the base of the container ofFIGS. 15 a-c;

FIG. 16 a: shows a side view of a container of FIG. 16 c according to analternative embodiment including inwardly projecting fluting throughLine J-J;

FIG. 16 b: shows a cross-sectional view of the base of the container ofFIG. 16 c through Line J-J;

FIG. 16 c: shows an underneath view of the base of the container ofFIGS. 16 a and 16 b with dotted contour section lines through lines G-Gand H-H;

FIG. 16 d: shows a perspective view of the base of the container ofFIGS. 16 a-c;

FIGS. 17 a-d: show side, side perspective, end perspective and end viewsrespectively of the container of FIG. 15.

FIGS. 18 a-d: show side, side perspective, end perspective and end viewsrespectively of the container of FIG. 16;

FIG. 19 a: shows a side view of a hot-filled container of an alternativeembodiment in its pre-collapsed condition;

FIG. 19 b: shows a cross-sectional view of the container of FIG. 19 athrough the line C-C.

DETAILED DESCRIPTION

The following description of preferred embodiments is merely exemplaryin nature, and is in no way intended to limit the invention or itsapplication or uses.

As discussed above, to accommodate vacuum forces during cooling of thecontents within a heat set container, containers have typically beenprovided with a series of vacuum panels around their sidewalls and anoptimized base portion. The vacuum panels deform inwardly, and the basedeforms upwardly, under the influence of the vacuum forces. Thisprevents unwanted distortion elsewhere in the container. However, thecontainer is still subjected to internal vacuum force. The panels andbase merely provide a suitably resistant structure against that force.The more resistant the structure the more vacuum force will be present.Additionally, end users can feel the vacuum panels when holding thecontainers.

Typically at a bottling plant the containers will be filled with a hotliquid and then capped before being subjected to a cold water sprayresulting in the formation of a vacuum within the container which thecontainer structure needs to be able to cope with. The present inventionrelates to hot-fill containers and a structure that provides for thesubstantial removal or substantial negation of vacuum pressure. Thisallows much greater design freedom and light weighting opportunities asthere is no longer any requirement for the structure to be resistant tovacuum forces which would otherwise mechanically distort the container.

As mentioned above and in the PCT specification, various proposals forhot-fill container designs have been put forward.

Further development of the hot-ill container of the POT specificationhas positioned an outwardly inclined and transversely oriented vacuumpanel between the lower portion of the side wall and the inwardly domedbase region. In this position the container has poor stability, insofaras the base region is very narrow in diameter and does not allow for agood standing ring support. Additionally, there is preferably provided adecoupling structure that provides a hinge joint to the juncture of thevacuum panel and the lower sidewall. This decoupling structure providesfor a larger range of longitudinal movement of the vacuum panel thanwould occur if the panel was coupled to the side wall by way of ribs forexample. One side of the decoupling structure remains adjacent thesidewall, allowing the opposite side of the decoupling structure,adjacent to an initiator portion to bend inwardly and upwardly. Thedecoupling structure therefore provides for increased deflection of theinitiator portion, allowing increased movement of the panel portionlongitudinally away from the previously outwardly inclined position,enabling the panel portion to fold inwardly relative to the containerand upwardly relative to the initial base position. The lower sidewallis therefore subjected to lower force during such inversion. During thisaction, the base portion is translated longitudinally upward and intothe container.

Further, as the panel portion folds inwardly and upwardly, thedecoupling structure allows for the vacuum panel to now form part of thecontainer base portion. This development has at least two importantadvantages.

Firstly, by providing the vacuum panel so as to form part of the baseafter folding, a mechanical force can now be provided immediatelyagainst the panel in order to apply inverting force. This allows muchgreater control over the action, which may for example be applied by amechanical pusher, which would engage with the container base inresetting the container shape. This allows increased design options forthe initiator portion.

Secondly, the transversely oriented vacuum panel is effectivelycompletely removed from view as it is forced from an outward position toan inward position. This means that there are no visible design featuresbeing imposed on the major portion of the side wall of the container inorder to incorporate vacuum compensation. If required therefore, themajor portion of the side wall of the present invention could have nostructural features and the container could, if required, replicate aclear wall glass container. Alternatively, as there will be little or novacuum remaining in the container after the panel is inverted, anydesign or shape can now be utilized, without regard for integrityagainst vacuum forces found in other hot-fill packages.

Such a manoeuvre allows for a wide standing ring to be obtained. Thedecoupling structure provides for the panel to become displacedlongitudinally so that there is no contact between any part of the panelor upwardly domed base portion with the contact surface below. Astanding ring is then provided by the lower sidewall immediatelyadjacent the decoupling structure.

Further, by gaining greater control over the inverting motion andforces, it is possible to allow the initiator portion to share the samesteep angle as the control portion. This allows for increased volumedisplacement during inversion and increased resistance to any reversionback to the original position.

Referring to the accompanying drawings, FIG. 1 shows, by way of exampleonly, and in a diagrammatic cross sectional view, a container in theform of a bottle. This is referenced generally by arrow 10 with atypical neck portion 12 and a side wall 9 extending to a lower portionof the side wall 11 and an underneath base portion 2. As will beappreciated by any skilled person, the sidewall 9 may be radiallyrecessed from touch bumper zones 450 that afford protection to the areabetween upper and lower touch zones during bottle to bottle contact andlabel zone protection. As will be further appreciated, the container mayalso comprise a plurality of annular strengthening rings or ribbings.These may be concentric around the container. These may be in the formof a large concave hoop ring 470, or in the form of smaller ribstructures 461. Such structures provide strength against vacuumdeformation during cooling of hot filled contents. Alternatively, suchstructures may be avoided altogether as shown in FIG. 8 a, where onlythe upper and lower touch bumper zones 450 are utilized.

The container 10 will typically be blow moulded from any suitableplastics material but typically this will be polyethylene terephthalate(PET).

The base 2 is shown provided with a plurality of reinforcing ribs 3 soas to form the typical “champagne” base although this is merely by wayof example only.

In FIG. 1 the lower side wall portion 11, which operates as a pressurepanel, is shown in its unfolded position circumscribing a ring orannular portion 6 positioned above the level of the bottom of the base 2and the standing ring or support section 4 for the container 10.

In FIG. 2 the lower side wall portion 11 is shown having folded inwardlyso that the ring or annular portion 6 is positioned below the level ofthe bottom of the base 2 and is forming the new standing ring or supportfor the container 10.

To assist this occurring, and as will be seen particularly in FIGS. 3and 4, immediately adjacent the ring or annular portion 6 there may be afirst wall portion or instep or recess 8 and a decoupling structure 13,in this case a substantially flat, non-ribbed region, which afterfolding enables the base portion 2 to effectively completely disappearwithin the bottom of the container and above the line A-A. Many otherconfigurations for the decoupling structure 13 are envisioned, however.

Referring now particularly to FIG. 5, the base 2 with its strengtheningribs 3 is shown surrounded by the bottom annular portion 11 of the sidewall 9 and the annular structure 13. The bottom portion 11 is shown inthis particular embodiment as having an initiator portion 1 which formspart of the collapsing or inverting section which yields to alongitudinally-directed collapsing force before the rest of thecollapsing or folding section. The base 2 is shown provided within thetypical base standing ring 4, which will be the first support positionfor the container 10 prior to the inversion of the folding panel.

Associated with the initiator portion 1 is a control portion 5 which inthis embodiment is a more steeply angled inverting section which willresist standing from the collapsed state.

Forming the outer perimeter of the bottom portion 11 of the side wall 9is shown the side wall standing ring or annular portion 6 whichfollowing collapsing of the panel 11 will provide the new containersupport.

To allow for increased evacuation of vacuum it will be appreciated thatit is preferable to provide a steep angle to the control portion 5 ofthe pressure panel 11. As shown in FIG. 6 the panel control portion 5 isgenerally set with an angle α varying between 30 degrees and 45 degrees.It is preferable to ensure an angle is set above 10 degrees at least.The initiator portion 1 may in this embodiment have a lesser angle β ofperhaps at least 10 degrees less than the control portion.

By way of example, it will be appreciated that when the panel 11 isinverted by mechanical compression it will undergo an angular changethat is double that provided to it. If the conical control portion 5 isset to 10 degrees it will provide a panel change equivalent to 20degrees. At such a low angle it has been found to provide an inadequateamount of vacuum compensation in a hot-filled container. Therefore it ispreferable to provide much steeper angles.

Referring to FIGS. 6 and 7, it will be appreciated that the controlportion 5 may be initially set to be outwardly inclined by approximately35 degrees and will then provide an inversion and angle change ofapproximately 70 degrees. The initiator portion may in this example be20 degrees. As a further example referring to FIG. 6A, the base 2 may berecessed to such an extent that the entire lower sidewall portion andbase are substantially or completely contained horizontally above thestanding ring 6 even prior to folding of the pressure panel 11.Preferably the pressure panel 11 includes a portion inclined outwardlyat an angle of greater than 10 degrees relative to a plane orthogonal toa longitudinal axis of the container when the pressure panel is in theinitial position, or about 100 degrees relative to the longitudinalaxis, and much steeper angles such as those described herein may beused.

Referring to FIGS. 8 a and 8 b, where the same reference numerals havebeen used where appropriate as previously, it is envisaged that inpossible embodiments of this invention the initiator portion may bereconfigured so that pressure panel 11 would provide essentially acontinuous conical area about the push-up 28, in this embodiment beingan inwardly recessed portion.

The initiator portion 1 and the control portion 5 of the embodiment ofthe preceding figures will now be at a common angle, such that they forma uniformly inclined panel portion. However, initiator portion 1 maystill be configured to provide the area of least resistance toinversion, such that although it shares the same angular extent as thecontrol portion 5, it still provides an initial area of collapse orinversion. In this embodiment, initiator portion 1 causes the pressurepanel 11 to begin inversion from the widest diameter adjacent thedecoupling structure 13. Such an arrangement is shown in FIGS. 19 a and19 b.

In the embodiment of FIGS. 8 a and 8 b the container side walls 9 are‘glass-like’ in construction in that there are no additionalstrengthening ribs or panels as might be typically found in a container,particularly if required to withstand the forces of vacuum pressure.Additionally, however, structures may be added to the conical portionsof the vacuum panel 11 in order to add further control over theinversion process. For example, the conical portion of the vacuum panel11 may be divided into fluted regions. Referring to FIGS. 8 a and 9especially, panel portions that are convex outwardly, and evenlydistributed around the central axis create regions of greater angularset 19 (δ) and regions of lesser angular set 18 (γ), may provide forgreater control over inversion of the panel. Such geometry providesincreased resistance to reversion of the panel, and a more evendistribution of forces when in the inverted position.

Referring to FIGS. 15 a-c and 17 a-d, convex or downwardly outwardlyprojecting flutes 18 are shown, providing inwardly directed creases 19there between. As discussed above, the creases may comprise a differentangulation to the longitudinal axis than other portions of the pressurepanel.

Concave or inwardly directed fluting arrangements are also envisioned,in addition to outwardly directed flutes. Inwardly directed flutes offerless resistance to initial inverting forces, coupled with increasedresistance to reverting back out to the original position. In this waythey behave in much the same manner as ribs to prevent the panel beingforced back out to the outwardly inclined position, but allow for hingemovement from the first outwardly inclined position to the inwardlyinclined position. Such inwardly or outwardly directed creases, flutesor projections function as ribs to increase or decrease the forcerequired to invert the panel. It will be appreciated that the mechanicalaction applied to invert the panel will be sufficient to overcome anyrib-strengthened panel, and when the mechanical action is removed therib-strengthened panel, for example by strong flutes, will be veryresistant to reversion to the original position if the container isdropped or shocked.

Referring to FIGS. 16 a-d and 18 a-d concave or upwardly inwardlyprojecting flutes are shown, the contour lines G and H of FIG. 16 cillustrating this concavity through two cross-sectional reliefs. Thisembodiment provides downwardly or outwardly directed creases 199 betweenthe inwardly directed flutes 188. The outwardly directed creases 199 inthis example create regions of lesser angular set than the regions 188.

Further embodiments comprising arrays utilizing both concave and convexflutes are also intended within the scope of the invention.

In the embodiment as shown in FIGS. 11 a-d the container may be blowmoulded with the pressure panel 20 in the inwardly or upwardly inclinedposition. A force could be imposed on the folding panel 20 such as bymeans of a mechanical pusher 21 introduced through the neck region andforced downwardly in order to place the panel in the outwardly inclinedposition prior to use as a vacuum container for example, as shown inFIG. 11 d.

In such an embodiment as shown in FIGS. 12 a-d, following the fillingand capping of the bottle and the use of cold water spray creating thevacuum within the filled bottle, a force could be imposed on the foldingpanel 20 such as by means of engaging a mechanical pusher 22 or thecreation of some relative movement of the centrally located push-upportion 28 of the bottle base relative to a punch or the like, in orderto force the panel 20 from an outwardly inclined position to an inwardlyinclined position. Any deformation whereby the bottle shape wasdistorted prior to inversion of the panel 20 would be removed asinternal volume is forcibly reduced. The vacuum within the container isremoved as the inversion of the panel 20 causes a rise in pressure. Sucha rise in pressure reduces vacuum pressure until ambient pressure isreached or even a slightly positive pressure is achieved.

It will be appreciate that in a further embodiment of the invention thepanel may be inverted in the manner shown in FIGS. 12 a-d in order toprovide a panel to accommodate internal force such as is found inpasteurization and the like. In such a way the panel will provide reliefagainst the internal pressure generated and then be capable ofaccommodating the resulting vacuum force generated when the productcools down.

In this way, the panel will be inverted from an upwardly inclinedposition FIGS. 11 a to 11 b to a downwardly inclined position as shownin FIGS. 12 a-d, except that the mechanical action is not provided. Theforce is instead provided by the internal pressure of the contents.

Referring again to FIGS. 12 a-d it will be seen that by the provision ofthe folding portion 20 in the bottom of the side wall 9 of the container10 the major portion of the side wall 9 could be absent any structuralfeatures so that the container 10 could essentially replicate a glasscontainer if this was required.

Although particular structures for the bottom portion of the side wall 9are shown in the accompanying drawings it will be appreciated thatalternative structures could be provided. For example a plurality offolding portions could be incorporated about the base 2 in analternative embodiment.

There may also be provided many different decoupling or hinge structures13 without departing from the scope of the invention. With particularreference to FIGS. 6 and 7, it can be seen that the side of thedecoupling structure 13 that is provided for the pressure panel 11 maybe of an enlarged area to provide for increased longitudinal movementupwards into the container following inversion.

In a further embodiment of the present invention, and referring to FIGS.13 and 14, it can be seen that the widest portions 30 of the pressurepanel 11 may invert earlier than the narrower portion of the controlportion 5. The initiator portion may be constructed with this in mind,to allow for thinner material and so on, to provide for the panel 11 tobegin inverting where it has the greater diameter, ahead of the narrowersections of the panel. In this case the portion 30 of the panel, whichis radially set more distant from the central axis of the containerinverts ahead of portion 5 to act as the initiator portion.

Where in the foregoing description, reference has been made to specificcomponents or integers of the invention having known equivalents thensuch equivalents are herein incorporated as if individually set forth.

Although this invention has been described by way of example and withreference to possible embodiments thereof, it is to be understood thatmodifications or improvements may be made thereto without departing fromthe scope of the invention as defined in the appended claims.

What is claimed is:
 1. A plastic container having a longitudinal axisand a base portion adapted for vacuum compensation, said containercomprising: an upper portion having an opening into said container, abody portion extending from said upper portion to a lower portion, thelower portion including the base portion that closes off an end of saidcontainer; said upper portion, said body portion and said lower portioncooperating to define a chamber within said container into which productcan be filled; said lower portion including a standing surface whichdefines a surface upon which said container is supported when filled andsealed, said base portion further including a central portion defined inat least part by a push-up portion located on said longitudinal axis ofsaid container and a pressure panel circumscribing said push-up portion,said pressure panel defining a substantially transversely orientedportion relative to said longitudinal axis, wherein the lower portionincludes a first wall portion or instep extending between the standingsurface and the upper portion to a hinge circumscribing the pressurepanel, and wherein the pressure panel defines a second wall portionextending away from the hinge towards the push-up portion, wherein afirst portion of the pressure panel is downwardly sloped at a firstangle of more than 100° relative to said longitudinal axis prior to saidcontainer being filled and sealed, and wherein a second portion of thepressure panel is sloped at a second angle that is less than the firstangle, and wherein the pressure panel and the push-up portion areconfigured to fold about the hinge from an outwardly inclined positionto an inwardly inclined position under a longitudinally directed forceto cause at least a portion of the pressure panel to invert andcompensate for a change of pressure induced within the container.
 2. Aplastic container as claimed in claim 1 wherein said pressure panel isadapted to cause said base to retract longitudinally into said bodyportion.
 3. A plastic container as claimed in claim 1 wherein saidinstep is recessed to an extent that the entire pressure panel iscompletely contained between the standing surface and the opening priorto folding of the pressure panel.
 4. A plastic container as claimed inclaim 3 having a recess defined therein when the pressure panel has beenrepositioned about the hinge.
 5. A plastic container as claimed in claim4 wherein said pressure panel is inclined at an angle of less than 135°relative to the longitudinal axis.
 6. A plastic container as claimed inclaim 1, wherein the body portion includes at least one concave hoopring to provide resistance against deformation.
 7. A plastic containeras claimed in claim 1, wherein a part of the body portion is adapted todeform inwardly under vacuum.
 8. A plastic container as claimed in claim6 having a plurality of hoop ring or rib structures.
 9. A plasticcontainer as claimed in claim 1 wherein the body portion comprises atleast one rib, the rib being oriented substantially perpendicular to thelongitudinal axis.
 10. A plastic container as claimed in claim 1 whereina portion of the base portion is configured to receive a force imposedby a mechanical pusher.
 11. A plastic container as claimed in claim 10wherein the portion of the base portion configured to receive a forceimposed by a mechanical pusher comprises the push-up portion.
 12. Aplastic container as claimed in claim 10 wherein said pressure panel isinwardly recessed from the standing surface to such an extent that theentire pressure panel is contained between the standing surface and theopening.
 13. A plastic container as claimed in claim 1 wherein saidpressure panel is inwardly recessed from the standing surface to such anextent that the entire pressure panel is contained between the standingsurface and the opening.
 14. A plastic container as claimed in claim 1wherein the container is manufactured from a plastic material of athickness suitable for withstanding the thermal shock of holding aheated liquid.
 15. A method of compensating for a change in pressureinduced within a plastic container according to claim 1 in which saidmethod includes applying a force to the said pressure panel to causefolding of the pressure panel and the push-up portion about the hingefrom an outwardly inclined position to an inwardly inclined position.16. A force applying means for performing the method of claim
 15. 17. Amethod as claimed in claim 15, comprising imposing a force on a portionof the base portion by a mechanical pusher.
 18. A force applying meansas claimed in claim 16 comprising a mechanical pusher.
 19. A plasticcontainer as claimed in claim 1 wherein the body portion includes asidewall portion, the sidewall portion being relatively free of ribstructures and adapted to deform inwardly under vacuum pressure.
 20. Aplastic container as claimed in claim 19 wherein the sidewall portion isforced radially outwardly following repositioning of the pressure panelfrom the outwardly inclined position to the inwardly inclined position.21. A plastic container having a longitudinal axis, an upper portionhaving an opening into said container, a body portion extending fromsaid upper portion to a base portion, said base portion closing off anend of said container, said container having at least one substantiallytransversely oriented pressure panel portion located in said baseportion, said pressure panel portion being configured to fold from alongitudinally outward position to an inward position to compensate fora change of pressure induced within the container, said pressure panelportion including an initiator portion and a control portion, whereinthe control portion is inclined by more than 100° relative to thelongitudinal axis and the opening, and the initiator portion is inclinedto a lesser degree than the control portion, and wherein a lower portionof the container includes a first wall portion or instep extendingbetween a standing surface and the upper portion of the container to ahinge circumscribing the pressure panel portion, and wherein the instepis recessed to such an extent that the entire pressure panel portion iscontained between the standing surface and the opening prior to foldingthe panel from the outward position to the inward position.
 22. Aplastic container as claimed in claim 21 wherein the body portionincludes a plurality of concave hoop ring or rib structures to resistdeformation and includes a bumper protection zone to facilitate bottleto bottle contact and label zone protection.
 23. A plastic container asclaimed in claim 22 wherein said pressure panel portion circumscribes apush-up portion adapted to engage with a mechanical pusher or the like.24. A plastic container as claimed in claim 22 wherein the container ismanufactured from a plastic material of a thickness suitable forwithstanding the thermal shock of holding a heated liquid.
 25. A plasticcontainer having a longitudinal axis and a base portion adapted forvacuum absorption, said container comprising: an upper portion having anopening into said container, a body portion extending from said upperportion to a lower portion to said base portion, said base portionclosing off an end of said container; said upper portion, said bodyportion and said base portion cooperating to define a receptacle chamberwithin said container into which product can be filled; said baseportion including a standing surface which defines a surface upon whichsaid container is supported, said base portion further including acentral portion defined in at least part by a push-up located on thelongitudinal axis of said container and an inversion pressure panelcircumscribing said push-up, said pressure panel defining a downwardlyshaped portion prior to said container being filled and sealed, saiddownwardly shaped portion having a first portion and a second portion,wherein the first portion is sloped relative to the longitudinal axis ofthe container at an angle of more than the second portion, wherein thefirst portion is sloped at an angle more than 100°, the push-up and thepressure panel being moveable to accommodate vacuum forces generatedwithin said container.
 26. A plastic container as claimed in claim 25wherein said body portion includes a plurality of ribs.
 27. A plasticcontainer as claimed in claim 25 wherein the push-up is a generallytruncated cone shape in cross section.